The purpose of this multicenter study is to test the safety of sputum induction and the reproducibility of the measurements of eosinophilic inflammation in induced sputum in 60 patient (10 per center) with moderately severe asthma. From a practical standpoint this proposed protocol will allow the Asthma Clinical Research Network (ACRN) to develop quality control measures for sputum induction and analysis for a subsequent study.